In recent years, the continued miniaturization of large scale integrated circuits (LSI) has lead to demands for techniques capable of processing ever finer structures. In response to these types of demands, testing has commenced into the formation of finer patterns using phase-separated structures that are formed by the self-assembly of a block copolymer containing mutually incompatible blocks bonded together.
In order to utilize this type of phase-separated structure of a block copolymer, a self-assembled nanostructure formed by microphase separation must be formed within only a specific region, and must be oriented in the required direction. In order to achieve this positional control and orientation control, processes such as graphoepitaxy, which controls the phase-separated pattern using a guide pattern, and chemical epitaxy, which controls the phase-separated pattern based on differences in the chemical state of the substrate, have been proposed.
For these block copolymers, block copolymers having a block formed from a repeating unit of a styrene and a block formed from a repeating unit of methyl methacrylate (PS-b-PMMA) are being widely investigated, and it is claimed that PS-b-PMMA is a material that can be used in the formation of very fine patterns down to approximately 13 nm.
Further, investigations are currently also being conducted into pattern formation methods using Si-containing block copolymers, which have been identified as materials potentially capable of realizing the formation of patterns of even finer dimensions. Block copolymer layers formed using these Si-containing block copolymers have low surface energy. Consequently, during the self-assembly of the block copolymer, controlling the surface state of the block copolymer layer is very important.
Accordingly, a method is being investigated in which phase separation is achieved by subjecting the block copolymer layer to an annealing treatment in a solvent atmosphere (solvent annealing). For example, a method of forming a pattern has been disclosed which uses a phase-separated structure obtained by forming a block copolymer layer having a block of a polyhedral oligomeric silsesquioxane (POSS) structure-containing structural unit on a substrate, and then subjecting the block copolymer layer to phase separation by carbon disulfide (CS2) solvent annealing (see Non-Patent Document 1).